Puzzling Human Relative Homo Naledi May Have Lived at the Same Time as Our Ancestors

Two views of an adult Homo naledi cranium found in the Lesedi Chamber of the Rising Star cave system in South Africa, where the remains of 15 individuals were discovered in a different cave in 2013.
Two views of an adult Homo naledi cranium found in the Lesedi Chamber of the Rising Star cave system in South Africa, where the remains of 15 individuals were discovered in a different cave in 2013.
Hawks et al. in eLife, 2017

It's tempting to think that evolution works in a straight line, with clearly defined, graduated steps from primitive to modern. We humans are especially prone to telling our own evolutionary story in this manner. Evolution doesn't work that way, though, and we aren’t even the end point of human evolution, but works in progress. (Personally, I hope we are amphibious and have fins in 3 million years. That would be awesome.)

The latest evidence for that essential truth comes from the Rising Star cave system in South Africa, where scientists say Homo naledi, the unusual hominid species they discovered there in 2013, is surprisingly young, living as recently as 236,000 years ago. That means it was one of various hominids wandering the Earth at the same time as the Neanderthals in Europe; the Denisovans in western Asia; the ancestors of the “hobbit,” Homo floresiensis; and, in Africa, potentially alongside the earliest members of our own species, Homo sapiens.

Moreover, the researchers found three more individuals in another chamber in the cave system, one of them with the most complete H. naledi skull discovered yet. (You can see it above.) Today the large team of researchers published a trio of papers documenting their results in the open-access journal eLife.

In 2015, we reported on the initial discovery of 15 sets of hominid remains found in the Dinaledi cave by a team of researchers led by paleoanthropologist Lee Berger. It was an unprecedented bounty of bones. Often, paleoanthropologists are reconstructing human evolutionary history from scant remains—a fragment of skull or jaw bone here, a femur or a finger there. But in the Dinaledi cave, there are at least 1500 bones, and likely a lot more, since only a small fraction of the cave was excavated by a half-dozen archaeologists—all female, all cavers, all slim enough to squeeze through a series of cave tunnels that narrowed to just 7 inches in one spot—who worked in extraordinary conditions to excavate the bones from a pitch-black cave nearly 100 feet beneath the surface.

The ancient creatures were no bigger than the small but formidable women who unearthed them. Slender and about 5 feet tall as adults, they would’ve weighed just under 100 pounds. Their bodies are a fascinating mosaic of primitive and modern: tiny, orange-sized brains housed in skulls with jaws and teeth closer to early Homo; shoulders suited for climbing trees but feet and ankles made for walking; hands potentially capable of making tools, but with fingers well-curved for tightly gripping tree branches.

The discovery made headlines worldwide. Most of us—whether scientist or science nerd—fascinated by the find had one question: How old were they?

DATING THE REMAINS

When H. naledi was first discovered, the researchers deliberately didn’t attempt to answer that question. Determining where a species fits into the evolutionary record based on its morphology is not an unusual approach, but it can also be misleading. In the past 1.5 years, other scientists have proposed ages for H. naledi that range from 100,000 to 2 million years ago.

In one of the current studies, researchers led by James Cook University geologist Paul Dirks conducted six dating tests to narrow the age range, including the paleomagnetic dating of calcite left behind by running water and a chemical analysis of three fossil teeth discovered in the cave using a technique called combined U-series and electron spin resonance (US-ESR) dating. From all the tests, they came up with an age range: they're most likely between 236,000 and 335,000 years old.

As eLife notes in a commentary on the study, “The estimated dates are much more recent than many had predicted, and mean that H. naledi was alive at the same time as the earliest members of our own species—which most likely evolved between 300,000 and 200,000 years ago. These new findings demonstrate why it can be unwise to try to predict the age of a fossil based only on its appearance, and emphasize the importance of dating specimens via independent tests.”

American Museum of Natural History paleoanthropologist Ian Tattersall echoed that sentiment to Mental Floss. “This is an object lesson in trying to date anything by what it looks like,” he says. While he doesn't find the age estimate surprising, he’s less convinced that H. naledi belongs in our Homo genus: “Anything as odd as this is always going to be tough to fit into both a phylogeny and a timescale,” he notes.

Did our ancestors interact with this oddball? We have no idea. But we do know that the picture of human evolution continues to expand in detail and complexity with every discovery like H. naledi.

Bioarchaeologist (and regular Mental Floss contributor) Kristina Killgrove, who teaches biological anthropology, human origins, and evolutionary theory at the University of West Florida, tells us that the long wait for H. naledi dates was “worth it.”

She says, “These dates reveal a much more complicated story of hominin evolution than ever before. We used to think of human evolution as a single lineage—the classic image of the progression from apes to humans. But H. naledi shows that palaeoanthropologists are onto something far more complex—and far more interesting! While these new dates won't make it into textbooks in time for the fall semester, I will certainly be updating my human evolution lectures this summer."

ONE NEW CAVE, THREE NEW BODIES

Whatever we have to learn about this cousin of humanity can only be helped by the other discovery reported today in eLife: 133 bones from three likely H. naledi individuals—two adults and one child—found in another cave in the Rising Star system. First spotted in 2013 by cavers, the bones were unearthed in three locations in a cave the researchers coined Lesedi. The two caves are found at the same depth, but they’re not directly connected.

As with the first expedition into the Dinaledi cave, the working conditions for the researchers weren’t easy: Wits University archaeologist Marina Elliott, who led the intrepid team of “underground astronauts” who excavated both sites, told National Geographic that while the Lesedi cave was slightly easier to reach than Dinaledi, she still had to excavate one set of remains from a 2-foot-wide alcove while laying on her chest, her shoulders pinned between rocks. “It’s extremely physically difficult,” she said. “I’ve tried to do a lot of yoga to get myself to be able to do it.”

Elliott would probably say it was worth it, though; the remains she excavated in that location yielded the most complete H. naledi skull so far discovered. Dubbed Neo (after the Setswana word for "a gift," not the The Matrix character), this adult has a larger skull—and therefore a larger brain capacity—than the other specimens so far discovered, but it falls within an expected range.

ARE THESE BURIALS OF A SORT?

One of the most contentious theories Berger and the team proposed when the first H. naledi fossils were discovered was that these bodies had been intentionally placed in the cave in some sort of death ritual. Berger and John Hawks, a paleoanthropologist at the University of Wisconsin, revisit that theory in the third paper published in eLife. They point out that the caves are difficult to access and aren’t obvious “death traps” that individuals could’ve accidentally fallen into. Nor did the remains show any signs of mass death, having been fed upon by carnivores or scavengers, or of having been flushed into the caves by a water system.

So how did they get there?

The researchers write, “We propose that funerary caching by H. naledi is a reasonable explanation for the presence of remains in the Dinaledi and Lesedi Chambers. Mortuary behaviors, while culturally diverse, are universal among modern human cultural groups. Such behaviors are not seen in living non-human primates or in other social mammals, but many social mammals exhibit signs of grief, distress, or other emotional response when other individuals within their social group die.”

They say that while there’s no evidence of symbolic thinking among H. naledi, such sophisticated thought isn’t necessarily a requirement for a death ritual. The “physical and social effects of the deaths of group members” could have been motivation enough.

“Such behavior may have many different motivations, from the removal of decaying bodies from habitation areas, to the prevention of scavenger activity, to social bonding, which are not mutually exclusive,” they note. “We suggest only that such cultural behavior may have been within the capabilities of a species that otherwise presents every appearance of technical and subsistence strategies that were common across the genus Homo.”

7 Historic European Castles Virtually Rebuilt Before Your Very Eyes

A reconstruction of Spiš Castle in eastern Slovakia.
A reconstruction of Spiš Castle in eastern Slovakia.
Budget Direct

While some centuries-old castles are still standing tall, others haven’t withstood the ravages of time, war, or natural disaster quite as well. To give you an idea of what once was, Australia-based insurance company Budget Direct has digitally reconstructed seven of them for its blog, Simply Savvy.

Watch below as ruins across Europe transform back into the formidable forts and turreted castles they used to be, courtesy of a little modern-day magic we call GIF technology.

1. Samobor Castle // Samobor, Croatia

samobor castle
Samobor Castle in Samobor, Croatia
Budget Direct

The only remaining piece of the 13th-century castle built by Bohemia’s King Ottokar II is the base of the guard tower—the rest of the ruins are from an expansion that happened about 300 years later. It’s just a 10-minute walk from the Croatian city of Samobor, which bought the property in 1902.

2. Château Gaillard // Les Andelys, France

Château Gaillard in Les Andelys, France
Château Gaillard in Les Andelys, France
Budget Direct

King Richard I of England built Château Gaillard in just two years during the late 12th century as a fortress to protect the Duchy of Normandy, which belonged to England at the time, from French invasion. It didn’t last very long—France’s King Philip II captured it six years later.

3. Dunnottar Castle // Stonehaven, Scotland

Dunnottar Castle in Stonehaven, Scotland
Dunnottar Castle in Stonehaven, Scotland
Budget Direct

Dunnottar Castle overlooks the North Sea and is perhaps best known as the fortress that William Wallace (portrayed by Mel Gibson in 1995’s Braveheart) and Scottish forces won back from English occupation in 1297. Later, it became the place where the Scottish monarchy stored their crown jewels, which were smuggled to safety when Oliver Cromwell invaded during the 17th century.

4. Menlo Castle // Galway City, Ireland

Menlo Castle in Galway City, Ireland
Menlo Castle in Galway City, Ireland
Budget Direct

This ivy-covered Irish castle was built during the 16th century and all but destroyed in a fire in 1910. For those few centuries, it was home to the Blake family, English nobles who owned property all over the region.

5. Olsztyn Castle // Olsztyn, Poland

Olsztyn Castle in Olsztyn, Poland
Olsztyn Castle in Olsztyn, Poland
Budget Direct

The earliest known mention of Olsztyn Castle was in 1306, so we know it was constructed some time before then and expanded later that century by King Casimir III of Poland. It was severely damaged during wars with Sweden in the 17th and 18th centuries, but its highest tower—once a prison—still stands.

6. Spiš Castle // Spišské Podhradie, Slovakia

Spiš Castle in Spišské Podhradie, Slovakia
Spiš Castle in Spišské Podhradie, Slovakia
Budget Direct

Slovakia’s massive Spiš Castle was built in the 12th century to mark the boundary of the Hungarian kingdom and fell to ruin after a fire in 1780. However, 20th-century restoration efforts helped fortify the remaining rooms, and it was even used as a filming location for parts of 1996’s DragonHeart.

7. Poenari Castle // Valachia, Romania

Poenari Castle in Valachia, Romania
Poenari Castle in Valachia, Romania
Budget Direct

This 13th-century Romanian castle boasts one previous resident of some celebrity: Vlad the Impaler, or Vlad Dracula, who may have been an early influence for Bram Stoker’s vampire, Dracula. It also boasts a staggering 1480 stone steps, which you can still climb today.

[h/t Simply Savvy]

Stegosaurus Tracks Discovered on Scotland’s Isle of Skye

Warpaintcobra, iStock via Getty Images
Warpaintcobra, iStock via Getty Images

Today, Scotland's Isle of Skye is a picturesque tourist destination. But 170 million years ago, it was home to one of the most iconic dinosaurs to ever roam the Earth. As The Guardian reports, paleontologists have found prehistoric footprints on the island that are believed to have come from a stegosaurus.

As researchers from the University of Edinburgh note in their new study published in the journal Plos One, the discovery marks the first evidence of stegosaurus on the Isle of Skye. The tracks, which were found in sedimentary rock on the east side of the island, are roughly the size of grapefruits. They follow a line stretching several feet, with a right-left sequence reflecting the gait of a four-legged animal. The shape of the prints themselves—larger, triangular back feet and slightly smaller front ones—match the skeleton of the armor-plated stegosaurus. If they do belong to stegosaurus, the 170-million-year-old find "represents one of the oldest fossil records of this major dinosaur group from anywhere in the world," the researchers write.

The stegosaurus made up just part of the recent Isle of Skye discoveries. Paleontologists also found prints with three-toes and claws from theropods (the group of carnivores that included T. Rex), and stubby three-toed tracks potentially belonging to ornithopods like duck-billed dinosaurs. Altogether, 50 new footprint fossils were found.

The Isle of Skye has long been known as a hotspot for dinosaur remains. During the Middle Jurassic period, the area had a swampy, subtropical climate that supported a vibrant wildlife population. The location where these latest tracks were discovered was a mudflat fringing a lagoon 170 million years ago. The mudflats were likely only around for a brief time before they were overtaken by the lagoon, indicating the species making up the batch of prints occupied the area around the same time. The researchers write, "As a result of this diversity, we can infer that a thriving community of dinosaurs lived in and near the subtropical lagoons of Middle Jurassic Scotland."

[h/t The Guardian]

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